A Content Delivery Network, or CDN, is a collection of proxy servers that are connected to the same origin server, and are geographically distributed relative to end users. Instead of utilizing a single server to respond to user requests, CDN edge servers are able to deliver content more effectively and efficiently to users based on their physical location. For example, if someone from Europe accesses your U.S.-hosted website, it would likely be done through a local U.K. server, not the U.S.-based server.
General CDN drawbacks
While CDNs have significant benefits and are a desirable solution to many companies, they do have their disadvantages, which we will outline in this article.
One such drawback is that you may find it challenging to find a reliable and efficient provider. CDN providers enter and exit the market quite frequently, although many solid players in the market have been around for years. It makes the price and performance evaluation difficult amongst the old and the new. Additionally, the application of CDN comes with a learning curve.
As a site owner, you do not necessarily need to understand all the technical detail and codes. However, some research will be required at your end to ensure that CDN and your site works in perfect harmony for performance. That is where the problem comes in since this factor can sometimes be a hit and miss, especially with less established CDN providers.
If your CDN provider lacks a good support system, you may find yourself in a pickle. A good CDN provider must always provide support 24/7 to monitor and ensure consistent performance.
Another potential general shortcoming of CDNs is their impracticality for certain websites. World-Wide-Web is a dynamic entity that is ever-evolving in the global market. Therefore, some websites that deal with true global traffic may find it difficult to take full advantage of the content delivery network, lacking the accurate mix of PoP locations.
SSL Performance Issues
SSL is infamous for inherent performance issues. It requires additional and frequent round-trip transfers between the browser and the server at the elementary level. Here is an example, just to give you an idea of what performance issues to expect.
Suppose a TCP handshake took 95ms. Now, this is RTT (Round-Trip Time) between a server in New Jersey and test location in Los Angeles. SSL negotiations require at least two additional round-trips between the server and the browser. Now, if your CDN servers aren’t configured properly for SSL negotiations with various browsers, you are more likely to experience a delay in performance.
Performance Issues a CDN Can’t Help With
Adding CDN to your infrastructure guarantees enhanced performance and reliability. But specific performance issues need more than just a CDN, such as your own web application servers. With many web applications, you may still experience a lack of performance should you not implement certain resources and configurations.
Some of the other performance arenas where a CDN may not be able to resolve problems are the following:
Inadequate Hardware Resources
Your main application server is known as an origin server, from where CDN pulls and caches the data. Now, if your server has low resources and starts getting a spike in traffic, in this case, even the most decent CDN will not be able to do enough to improve your performance. You will need a faster server with ample resources to handle increased traffic.
Low resources, such as hard drive power, CPU power, and RAM, reduce the efficacy of your web application. Whenever you consider the integration of a CDN into your infrastructure, always ensure that your application server has sufficient resources to handle the traffic and data transferred to your CDN network.
Sluggish Network Resources
Whenever a CDN server pulls data from your main application server, the speed at which the content transfers depends on several factors, such as your network resources. Lack of network speeds to match the demands or to have low bandwidth from your sharing host both can hinder your performance by slowing down data transfer.
Bandwidth is an essential element to enable the transference of large content files across data centers on the CDN network from your network. Most ISPs offer proficient bandwidth for consumers. However, local networks hosting web applications must have adequate bandwidth installed to transfer large content files on local networks.
Third-Party Software
Although being dependent on applications is not a new concept to the developers, but most third-party software installations and additions must get tested for performance. Some issues can actually become the driving force behind affecting the entire web application performance. Performance issues may also arise from the installation of third-party tools on web servers.
In this instance, a CDN will not help to give you the answers you’re looking for. You will likely need to test any third-party software, tools, and dependencies in a simulated environment before installing them over your infrastructure, as well as in the production environment. On top of that, interaction and performance with software must be tested with your critical servers.
Cache Settings
Although your CDN edge server is responsible for caching and delivering content, your websites and applications also require configuration to cache static content. Static content may include CSS code, JavaScript, and HTML, which does not change frequently. As this content is static, you do not need to conduct a full lookup on your server to generate an appropriate server response.
In some scenarios, the administrators may have incompatible cache settings, which can mess up overall cache configurations. You can test these server responses post-deployment in staging or production environments.
Once you have configured these settings, you can always re-test your websites and applications. You can use tools, such as the Website Speed Tool from Dotcom-Monitor or other tools like Google PageSpeed Insights. Only with the correct CDN configuration and the right server resources will your website be able to perform efficiently irrespective of spikes in popularity and seasonal traffic.
Why Invest in a CDN at All?
With all of the considerations and drawbacks, it might seem unreasonable to invest in a CDN. However, a CDN combined with a reliable monitoring solution can provide you with a cost-effective way to track the required data and metrics to help you ensure that the CDN you invested is performing as intended – and speeding up the delivery of all that great website content to your users. Additionally, monitoring can ensure your CDN is meeting your SLAs. Some Important CDN metrics to monitor include the following:
- Server response time. The ability to track the response time from a CDN server can help you prove the business case for investing in a monitoring solution.
- Individual page element load times. Just measuring page time load is not always enough to give you the full picture. If there’s an issue, you want to know exactly what elements are causing the issue and where the problem is. A monitoring solution should reach deep into web pages to show you what’s going on and give you those metrics like individual response time.
- Host speeds. In an CDN, content is obviously distributed across several servers, making it more difficult to determine the specific areas where problems lie. Monitoring your CDN will help your teams find and locate issues that they can then take to their CDN provider to help resolve.
A CDN Still Pays Off in the End
A CDN undoubtedly presents numerous attractive benefits to the right websites, such as enhanced stability, faster page loading time, improved SEO, and user experience. However, it may present challenges requiring a significant amount of effort and time to address performance issues. All these tradeoffs are worth exploring before you go all-in with the implementation of a CDN or your business. Conduct thorough research; evaluate your infrastructure and compatibility and run simulations to check whether CDN can actually help your performance, or it may just be another expense on your list.
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